In Patent Literature 1, disclosed is a signal processing method when a photon such as X-ray is incident to a sensor including a plurality of sensing areas. Patent Literature 1 recites a phenomenon in which electric charge generated in a sensor by the photon incidence does not stay only within one pixel and spreads in a plurality of pixels (charge share). According to the method disclosed in Patent Literature 1, a pixel (center pixel) having a charge amount exceeding a threshold is first detected from among the plurality of pixels in order to specify an incident position and intensity of the photon even in the event of the charge share. Further, a plurality of combination patterns is considered as combinations of the center pixel and peripheral pixels. The charge amounts in the pixels included in each of the combination patterns are added and the largest added value is output as a charge amount in the center pixel.